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Old 15-02-2018, 17:14   #1
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Battery charging by engine

We have agm batteries on board.

Currently charging under the main engines.

1500 rpm per engine.

What sort of peak voltage should we expect?

We are only seeing 13.6 volts after 2 hours.

What do you think?

Does this sound about right.

Thanks
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Old 15-02-2018, 19:25   #2
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Re: Battery charging by engine

It's not an appropriate way to charge AGM batteries. They need to get to a 100% state of charge at least a few times a week. The charging voltage should get to the manufactures specd absorption voltage, probably near 14.6v.
Unless you do lots of long motoring it is hard to get AGMs to 100% just by engine. Solar helps a lot.
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Old 16-02-2018, 01:39   #3
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Re: Battery charging by engine

What year is your boat ? Volvo or Yanmar ? How many Ah is your battery ? What state of charge (SOC) ?

If it's older Yanmar then the alternators are not very powerful and it will take a long time recharging depleted batteries. 13.6V after 2 hours may then as expected.

You may have a battery monitor / amp meter: how many amps does it show going to the battery ?

AGM technology may not have been the best choice. It seems there is a consensus that they will not last as long as standard flooded lead acid or Gel. Unless maybe being recharged to 100% very frequently, which doesn't seem to be your case.
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Old 16-02-2018, 04:00   #4
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Re: Battery charging by engine

The boat is a 2016. Until we get the generator impeller replaced later today, that's all we have. The bank is around 700 ah. Solar is pending next month.
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Old 16-02-2018, 09:26   #5
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Re: Battery charging by engine

Out of interest, did you just discover the broken impeller or did the generator bring up fault alarm and stop?

Do you have the lagoon fitted lift pump between the raw water inlet and the generator?

good luck.
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Old 16-02-2018, 09:29   #6
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Re: Battery charging by engine

You are unlikely ever to charge your battery fully using the engine alternators alone. You would need to change the regulators to'smart' ones that could be adjusted to fit the nature of your AGM's. When the motors start, they will initially have a high rate of charge which will quickly diminish.
Alternators can easily get too hot and burn out and are really designed just to quickly get the starter battery bank to a level sufficient to start the engines again. 13.6v after 2 hours is reasonable considering that your bank is 700AH.
Say you are charging at 40A total, it would take you 9 hours to charge your battery if it was half flat.
Alternators are not designed to fully charge a battery.
Solar panel controllers can be set for battery type and if they are 'smart' can give the differing voltages needed to maintain the charge in a battery.
When your generator is repaired and gives out AC, I would always connect it to the smart battery charger because it will alter the output voltage to the battery to go through the absorption, bulk, and float charging periods, which are all at differing voltages.
If you have starting batteries and domestic batteries (which is advisable) they have different charging regimes. Download the book on batteries from Victron/Mastervolt for further guidance, as the subject is vast and will depend on your specific yachts requirements.Best of luck.
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Old 16-02-2018, 10:18   #7
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Battery charging by engine

PaulinOz raises the issue of problems with the Generator that there have been lots of discussions in the forums about. Here are the problems and my solutions;

1. Impeller starts dry and blades rip off, after 150hrs, and jam in the heat exchanger. If you find missing blades you must clear the heat exchanger. My solution that has been 100% effective is buy the Globe Run-dry impellers.

2. The raw water anode must be replaced every 18 months, max. It is hard to access behind the heat exchanger. I open all the surrounding panels, take the top off and with some contortion can get a 10mm socket on to it.

3. The raw water inlet has a NRV (non return valve). I have tried two and both jammed with weed, shells and a small fish! I have removed the NRV as it does not work anyway and maybe the start takes another 5 seconds. Hence good to have a run-dry impeller!

Cheers
Dave
PS yep the standard 80A alternators only give 40A. I installed a smart charger but got very random results. Now have 960W solar on Bimini and get up to 53A change on a sunny day. Solar is best.
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Old 16-02-2018, 11:59   #8
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Re: Battery charging by engine

Yes you can charger very effectively with your main engine, as effective as your generator.
IF you have good externally regulated alternators and a good three stage regulator.
Likely you have I assume stock alternators and are internally regulated, if so then no, you canít effectively charge your batteries. You can maintain a charge, but not a whole lot of real charging will occur as they are not Iím sure putting out absorption voltage.
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Old 16-02-2018, 12:01   #9
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Re: Battery charging by engine

I deleted my water pump">raw water pump entirely and instead use an AC March air conditioner pump, thousands of hours mean time between failure and no impeller blades to fail, and the pump only runs when the generator is making AC power so you canít accidentally flood the engine with seawater.
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Old 16-02-2018, 12:38   #10
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Re: Battery charging by engine

Quote:
Originally Posted by a64pilot View Post
I deleted my raw water pump entirely and instead use an AC March air conditioner pump, thousands of hours mean time between failure and no impeller blades to fail, and the pump only runs when the generator is making AC power so you canít accidentally flood the engine with seawater.
I start my genset and it runs for about a minute before load comes on so for that time there would be no water.
Is that what yours does?
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Old 16-02-2018, 12:42   #11
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Re: Battery charging by engine

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Originally Posted by DavefromNZ View Post
My solution that has been 100% effective is buy the Globe Run-dry impellers.
Had to google them


Globe Blue Run Dry impellers - SailNet Community
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Old 16-02-2018, 13:20   #12
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Re: Battery charging by engine

I have never been able to understand why any manufacturer of marine engines would want to fit a Jabsco. THere are good alternatives. How many times is a boat stranded in the harbour or incapacitated at sea because of that silly impellor?
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Old 16-02-2018, 14:05   #13
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Re: Battery charging by engine

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I start my genset and it runs for about a minute before load comes on so for that time there would be no water.
Is that what yours does?
You dummy Simi
There's green coolant circulating through the motor so a minute or two before the raw water cooling kicks in will be fine.
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Old 16-02-2018, 14:58   #14
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Re: Battery charging by engine

Re Generator impellers for L450. We just took the impeller out. The lift pump (in the bilge) that goes on when you prime or start the generator has sufficient water flow without needing the impeller on the engine, done 1000 hours so far this way. No need to reconfigure anything.

For check valves that get clogged we inserted a spin on transparent strainer between the through hull inlet and the check valve.
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Old 16-02-2018, 15:10   #15
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Re: Battery charging by engine

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Originally Posted by Simi 60 View Post
I start my genset and it runs for about a minute before load comes on so for that time there would be no water.

Is that what yours does?


Assuming your generator comes on line automatically, that one minute is the relay box, itís purpose is of course to prevent you backfeeding power back into the shorepower connection, so the Boat can only be connected to either the shorepower cable or the generator, not both. Box I installed can have either a 1min delay, which I left so that the generator has a chance to stabilize before power is switched to the boat, or it can be instant, I actually wonít put any load on the generator for a few minutes until it warms up, but I do that manually.
However the pump I wired direct to the generator output, so as soon as itís up to RPM, the pump is on, but the boat is not connected for 1 minute. That way even if my AC main circuit breaker is open, the pump is getting power, or the relay box goes bad, the pump is getting power.
The generator starts, and itís louder for about three sec, then you can tell the water begins to flow as the exhaust note changes, so you learn to listen for that change to ensure water is flowing, or of course just go look, but without the water, mine is much louder, your not missing that if you listen.
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